Ligament anchoring device

ABSTRACT

A device including an elongate body (15) with anti-rotation projections on the peripheral side surface thereof and a generally flat side bearing surface (20) for engaging one side of a bone rod (5) forming the end of a ligament (4). The body (15) comprises an axial hole having a tapered internal seat and being engaged by a screw. Slots (24) enable the body (15) to be expanded by the axial screw. When the body (15) is expanded (13, 14), the bone rod (5) is locked in place in a hole (7) formed in the bone (2). Reliable and easily performed and adjusted ligament anchoring may thus be achieved.

TECHNICAL FIELD OF THE INVENTION

The present invention concerns means for attaching a ligament to a bone.

In orthopedic surgery it is frequently necessary to attach the end of aligament to the bone of a patient, whether this is a ligament prosthesiscomprising an artificial ligament or a living ligament taken fromanother part of the body of the patient.

Various anchoring techniques have been used until now. For example,document FR-A-2 696 925 describes an anchoring technique in which a holeis made in the bone tissue of the bone to which the ligament must beattached, a graft is taken consisting of a ligament central partattached to bone end parts in the form of a rod, one of the bone rods isinserted into the hole in the bone tissue and an axial screw is insertedin parallel into the same hole, beside the bone rod, applying forcelaterally both to the bone rod and to the wall of the bone tissue hole.The anchorage is effective but the surgeon cannot easily adjust theaxial tension in the ligament during implantation and, more importantly,there is the risk of the ligament being weakened by the edges of thescrew, which cut into it, in particular when the ligament end is to beanchored into a blind hole from the interior of the joint. DocumentEP-A-0 596 829 describes a similar anchorage with an oblique screw whichadditionally clamps the end of the ligament, which can also weaken theligament.

In document FR-A-2 586 927 the end of the ligament is hollow and tubularand a conical plug is inserted into the hollow tube to press the wall ofthe tubular part of the ligament against a conical portion of a hole inthe bone tissue. Clearly an anchorage of the above kind is not suitablefor anchoring a living ligament, in which it is not easy to form atubular end, and the surgeon will obviously find it very difficult toadjust the tension in the ligament during implantation.

In document EP-A-0 596 177 the end of the ligament is immobilized in ahole in the bone tissue by a transverse clamping screw. The screw canshear the end of the ligament and weaken the anchorage.

In document FR-A-2 671 717 a device is provided to anchor the end of thean artificial ligament prosthesis consisting of a wick or braid of aphysiologically compatible woven material. The anchorage is provided bya pin having an expandable cylindrical shank partially inserted into ahole in the bone and receiving a screw in an axial bore in the shank toexpand the shank radially and immobilize it in the hole. The prosthesisend fits around the part of the shank projecting out of the bone and ispressed against the external surface of the bone by the front face of acylinder having a diameter greater than that of the shank and forming ahead on the pin. The prosthesis is external to the bone and extendsradially of the shank and of the hole in the bone. An anchorage of theabove kind is not suitable for retaining a living ligament, which isweakened by the relatively large diameter hole needed in the ligamentfor the shank to pass through.

Document DE-U-92 10 031 concerns an expandable plug for anchorage inconcrete. This is a technical field remote from that of the presentinvention. The plug has an expandable shank the outside surface of whichhas a square section to define longitudinal edges opposing rotation inthe hole in the concrete. Expansion is effected in a diagonal directionby a central axial screw by virtue of four longitudinal slotsperpendicular to the four side faces. Thus the side faces are not planeand are interrupted by the longitudinal slots. In the conventionalmanner, the object anchored by the plug remains outside the concrete.

SUMMARY OF THE INVENTION

The problem addressed by the present invention is that of designing anew ligament anchoring device that assures an effective and reliableanchorage without risk of shearing the ligament and which makes it veryeasy for the surgeon to adjust the tension in the ligament duringimplantation without requiring any additional prestressing of theligament.

Another object of the invention is to design an anchoring device of theabove type which, once fitted, does not have any part projectingexternally of the bone.

To achieve the above and other objects, a ligament anchoring device inaccordance with the invention, for fixing the end of a ligament to abone, comprises:

an elongate body along a longitudinal axis and delimited by a peripheralside surface, a proximal end and a distal end,

a longitudinal axial hole in the body open at its proximal end at least,

at least one interior constriction of the axial hole,

longitudinal slots through the body and distributed around the perimeterof its peripheral surface at least in the vicinity of the area occupiedby the constriction of the axial hole,

an axial core housed in the axial hole in the body and movablelongitudinally to bear against the constriction of the axial hole on acontact surface adapted to expand the body by this means, and

means accessible from the proximal end of the body for selectivelymoving the axial core in the longitudinal direction,

anti-rotation projections are formed on the external surface of the bodyto prevent it rotating in the hole in the bone tissue,

a generally flat lateral bearing face forms a part of the peripheralside surface of the body and is adapted to bear against a side of theend of the ligament inserted side by side with the body in a hole in thebone tissue opening onto the exterior surface of the bone,

the peripheral side surface of the body has a generally constantcross-section throughout its length.

In a first embodiment:

the axial hole has an internally screwthreaded rigid portion with nolongitudinal slots,

the axial core and the means for moving it axially comprise a screw theshank of which has a screwthreaded portion functionally inserted in thescrewthreaded portion of the axial hole, the screw having a portionadapted to bear, during screwing, against a conical constriction of theaxial hole and thereby expand the body.

In a first variant of the first embodiment the larger diameter screwportion is formed by the distal screw end opposite the screw head. Inthis case, the screw head preferably has a polygonal cross-section withrounded corners forcibly inserted at the end of screwing into a proximalend portion of the body with longitudinal slots through it and having adiameter less than that of the screw head.

In a second variant of the first embodiment the larger diameter screwportion is formed by the proximal screw head inserted in a proximalconical portion of the axial body hole.

In a second embodiment:

the axial core slides freely and longitudinally in the axial hole and iscoupled to the body by means for preventing axial rotation,

the axial core has a screwthreaded axial bore,

a screw with a screwthreaded shank and a proximal head is inserted inthe axial hole in the body with its head in axial bearing engagementagainst the proximal end of the body and with its shank functionallyinserted in the screwthreaded axial bore of the axial core so thatrotation of the screw moves the axial core axially and expands the body.

In a first variant of the second embodiment the screw head has a conicalbearing face engaged against a second conical portion of the axial holeassociated with second longitudinal slots constituting a secondexpandable portion of the body.

The conical portions can have a circular cross-section, constituting acircular conical portion, or can have a polygonal cross-section,constituting a pyramidal portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willemerge from the following description of particular embodiments givenwith reference to the accompanying drawings, in which:

FIG. 1 is a part-sectional schematic side view of a ligament prosthesislinking two bone ends and anchored by two ligament anchoring devices inaccordance with the present invention;

FIG. 2 is a sectional side view to a larger scale of one of the twoligament anchoring devices from FIG. 1;

FIG. 3 is a schematic view in cross-section taken along the line A--A inFIG. 2;

FIG. 4 is a side view in longitudinal section of a first embodiment of aligament anchoring device of the present invention;

FIG. 5 is a side view in longitudinal section of a variant of the FIG. 4embodiment of a ligament anchoring device;

FIG. 6 is a side view in longitudinal section of a second embodiment ofa ligament anchoring device of the present invention;

FIG. 7 is a side view in longitudinal section of a variant of the FIG. 6embodiment of a ligament anchoring device;

FIG. 8 is a side view in longitudinal section of another variant of theFIG. 6 embodiment of a ligament anchoring device;

FIG. 9 is a side view in longitudinal half-section of an anchor body inanother variant of the first embodiment of the present invention;

FIG. 10 is an end view of the anchor body from FIG. 9;

FIG. 11 is a part-sectional side view of an expansion screw that fitsthe anchor body from FIG. 9; and

FIG. 12 is an end view of the screw head from FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the example shown in FIG. 1 a ligament prosthesis 1 is adapted toconnect a first bone 2 to a second bone 3. The ligament prosthesis 1comprises a central ligament 4 attached at its first end to a first bonerod 5 and attached at its second end to a second bone rod 6. Theligament prosthesis 1 is inserted in two holes 7 and 8 respectivelyformed in the first bone 2 and in the second bone 3. Near the externalsurface 9 or 10 of the corresponding bone 2 or 3 the respective hole 7or 8 has an enlarged section enabling insertion of an anchoring device11 or 12 in accordance with the invention parallel to the axis of thehole 7 or 8 and alongside the corresponding bone rod 5 or 6.

As can be seen more clearly in FIG. 2, the hole 7 formed in the bonetissue of the bone 2 and extending longitudinally along the axis II--IIreceives a portion of the ligament 4, the bone rod 5 that terminates theligament 4 and the anchoring device 11. The bone rod 5 is elongate andthe anchoring device 11 is also elongate. They are disposed side by sidein the hole 7, parallel to the axis II--II of the hole. The anchoringdevice 11 is a selectively expandable element in the radial direction asshown by the arrows 13 and 14 for wedging the bone rod 5 into the bone2. The anchoring device 11 is preferably expanded progressively so as toenable the surgeon to adjust the position of the bone rod 5 in the hole7 easily and accurately in order to adjust the tension in the ligament 4during implantation. The expansion of the anchoring device 11 ispreferably reversible, enabling the surgeon to reduce the expansion torelease the bone rod 5 temporarily if further adjustment of the tensionin the ligament is necessary.

In all the embodiments shown hereinafter the anchoring device 11comprises an elongate body 15 extending along a longitudinal axis I--Iand delimited by a peripheral side surface 16, a proximal end 17 and adistal end 18.

Anti-rotation projections are formed on the external surface of the body15, for example on the peripheral side surface 16 of the body 15, toprevent it rotating in the hole 7 in the bone tissue. In particular, asshown in FIG. 3, the body 15 can have a substantially constant polygonalsection throughout its length, for example a square section, thus havingedges like the edge 19 constituting an anti-rotation projectionpreventing the body 15 rotating in the hole 7 in the bone tissue.Alternatively, as shown in FIG. 2, front projections 119 can be providedon the distal front face 18 of the body 15.

Part of the peripheral side surface 16 of the body 15 is generally planeand continuous to form a generally flat side bearing face 20. This sidebearing face 20 is adapted to bear against a side 21 of the bone rod 5forming the end of the ligament 4.

A longitudinal axial hole 22 is formed in the body 15 and is open atleast at its proximal end 17. The axial hole 22 has at least one conicalportion 23. Longitudinal through slots, like the slot 24, aredistributed around the perimeter of the peripheral surface 16 of thebody 15 near the area occupied by the conical portion 23 of the axialhole 22. In FIG. 4, for example, slots like the through slot 24 (FIGS. 2and 3) are distributed over a length F on either side of the conicalportion 23. In FIGS. 2 and 5 the slots, like the slot 24, are disposedfrom the proximal end 17 over approximately two-thirds of the length ofthe body 15 towards the distal end 18, the conical portion 23 occupyingsubstantially the same length F. FIG. 3 shows an embodiment with fourslots 24 in cross-section taken along the line B--B in FIGS. 4 through8. It can be seen that the slots 24 are advantageously disposeddiagonally to connect the apexes of the square section with the resultthat the lateral bearing face 20 is continuous, i.e. free of slots.

In all the embodiments an axial core is accommodated in the axial hole22 in the body 15 and can be moved longitudinally to bear against theconical portion 23 of the axial hole 22 and thereby expand the body 15.Means accessible from the proximal end 17 of the body 15 move the axialcore selectively in the longitudinal direction to expand or contract thebody 15.

In the FIG. 4 embodiment the axial hole 22 has an internallyscrewthreaded rigid portion 124 with no longitudinal slots. The axialcore and the means for moving it axially are then in the form of a screw25 the shank of which has a screwthreaded portion 26 functionallyinserted in the screwthreaded rigid proximal portion 124 of the body 15with the axial hole 22, the distal end 27 of the screw 25 opposite thescrew head 28 having a conical portion inserted in the conical portion23 of the axial hole 22 to expand the slotted intermediate part F of thebody 15 when the screwthreaded portion 26 of the screw 25 is screwedinto the screwthreaded portion 124 of the body 15.

The screw 25 can have a head 28 with means for engaging a screwdrivingtool, for example a polygonal section blind axial hole.

In the embodiment shown in FIG. 4 the screw head 28 has a conicalbearing face 29 with radial striations 30 engaging at the end ofscrewing against a corresponding striated conical proximal face 31 ofthe body 15 to oppose unscrewing of the screw 25.

Alternatively, the proximal end 17 of the body 15 and the screw head 28can be slotted to render them flexible to produce a reversible clippingengagement opposing unintentional unscrewing of the screw.

In the variant shown in FIG. 5 the conical portion 23 of the axial hole22 is the hole portion nearest the proximal end 17 of the body 15 andthe rigid portion 124 of the body 15 is near the distal end 18. Theproximal head 28 with the flared bearing face of the screw 25 bearsagainst the proximal conical portion 23 of the axial hole 22 in the body15. The slots extend along the proximal portion F of the body 15.

In the FIG. 6 embodiment an axial core 32 slides freely in thelongitudinal direction in the axial hole 22 and is coupled to the body15 by means for preventing axial rotation. For example, the axial core32 has on its peripheral surface a radial immobilizing lug 33 engaged inone of the slots 24 in the body 15 to prevent it rotating. The axialcore 32 has a screwthreaded axial bore 34. A screw 35 with ascrewthreaded shank 36 and a proximal head 37 is inserted in the axialhole 22 in the body 15. The head 37 bears axially against the proximalend 17 of the body 15. The screw shank 36 is functionally inserted inthe screwthreaded axial hole 34 in the axial core 32. Rotating the screw35 moves the axial core 32 axially and expands the body 15 because theaxial core 32 is in bearing engagement inside the conical part 23 of theaxial hole 22 in the body 15. The slots like the slot 24 are in thedistal part F of the body 15 including the conical part 23 of the axialhole 22. In the FIG. 6 embodiment the screw head 37 has a shoulder andbears against a front face of the proximal end 17 of the body 15.

The variant shown in FIG. 7 includes the same means as the FIG. 6embodiment and corresponding parts are identified by the same referencenumbers.

In the FIG. 7 variant the difference is that the screw head 37 has aconical or flared bearing face 38 engaged against a second conicalportion 39 of the axial hole 22 associated with second longitudinalslots F2 constituting a second expandable portion of the body 15. Thebody 15 therefore has a first expandable portion F near the distal end18 and a second expandable portion F2 near the proximal end 17.

FIG. 8 shows a variant of the FIG. 6 embodiment in which correspondingparts are identified by the same reference numbers. The modification isin the particular shape of the axial core 32 which is generallyspherical in the FIG. 6 embodiment and generally frustoconical in theFIG. 8 variant.

In all the embodiments shown the peripheral side surface 16 of the body15 advantageously has anti-slip projections opposing axial sliding ofthe body 15 in the hole 7 in the bone tissue and simultaneously opposingrelative axial slipping between the body 15 and the bone rod 5 to beimmobilized and forming the end of the ligament 4.

The embodiment shown in FIGS. 9 through 11 relates to the embodimentshown in FIGS. 3 and 4. To avoid the necessity to repeat the descriptioncorresponding parts of the two embodiments are identified by the samereference numbers.

They include the elongate anchor body 15 along the longitudinal axisI--I with its peripheral side surface 16 having a generally flat sidebearing face 20, an axial hole 22 with a constriction 23 between arelatively narrower distal hole portion 122 and a relatively widerproximal hole portion 222, and four slots 24. The distal portion 122 ofthe hole 22 is formed by the crossing over of the four diagonal slots24, as can be seen more clearly in FIG. 10. The diagonal slots 24 extendover the length of the anchor body 15 occupied by the distal portion 122of the hole 22 between the distal end 18 and the constriction 23.

At the proximal end the constriction 23 is flanked by a larger diameterarea 322 of the axial hole 22 favoring radial elastic deformation of thebody 15 in the area of the constriction 23. As can be seen in FIG. 10,the exterior surface 16 of the anchor body 15 is generallyparallelepiped shape with a square section and anti-slip projections 116in the distal portion in the form of triangular section circular ribs.

The anchor body 15 has a proximal end portion 215 with longitudinalslots through it like the slots 216 and 217 and the inside diameter D1of which optionally varies to form a slight conicity with the apex atthe distal end.

In this embodiment the axial core is also a generally cylindrical bodyscrew 25 with a conical distal end 27 with a cone angle of approximately60° adapted to be inserted into the constriction 23 in the anchor body15. The proximal end of the screw 25 is a head 28 with a polygonalcross-section with rounded corners, for example a square section asshown in FIG. 12, forcibly inserted at the end of screwing into theproximal end portion 215 of the anchor body 15. The diameter D2 of thetwo diagonals of the screw head 28 is greater than the diameter D1 ofthe interior passage in the proximal end portion 215 of the body.Elastic deformation of the proximal end portion 215 with longitudinalslots 216 and 217 through it prevents rotation of the screw 25 at theend of screwing.

Accordingly, a ligament prosthesis in accordance with the inventioncomprises an anchoring device 11 inserted side by side into a hole 7 inthe bone tissue with a bone rod 5 forming the end of a ligament 4.

The anchoring device of the invention is made from biocompatiblematerials, possibly bioresorbable materials. The anchor body 15 can bemade of polyethylene, for example, and the expansion screw 25 can bemade of stainless steel, titanium or polyethylene.

The present invention is not limited to the embodiment explicitlydescribed but encompasses variants and generalizations thereof withinthe scope of the following claims.

I claim:
 1. A ligament anchoring device for fixing the end (5) of aligament (4) to a bone (2), comprising:an elongate body (15) along alongitudinal axis (I--I) and delimited by a peripheral side surface(16), a proximal end (17) and a distal end (18), a longitudinal axialhole (22) in the body (15) open at its proximal end (17) at least, atleast one interior constriction (23) of the axial hole (22),longitudinal slots (24) through the body (15) and distributed around theperimeter of its peripheral surface (16) at least in the vicinity of thearea occupied by the constriction (23) of the axial hole (22), an axialcore (25, 32) housed in the axial hole (22) in the body (15) and movablelongitudinally to bear against the constriction (23) of the axial hole(22) on a contact surface adapted to expand the body (15) by this means,means (25, 35) accessible from the proximal end (17) of the body (15)for selectively moving the axial core (25, 32) in the longitudinaldirection (I--I), wherein:anti-rotation projections (19) are formed onthe external surface (16) of the body (15) to prevent it rotating in thehole (7) in the bone tissue, a generally flat lateral bearing face (20)forms a part of the peripheral side surface (16) of the body (15) and isadapted to bear against a side (21) of the end (5) of the ligament (4)inserted side by side with the body (15) in a hole (7) in the bonetissue opening onto the exterior surface (9) of the bone (2).
 2. Ananchoring device according to claim 1 wherein:the axial hole (22) has aninternally screwthreaded rigid portion (124) with no longitudinal slots(24), the axial core and the means for moving it axially comprise ascrew (25), the screw having a shank, the shank having a screwthreadedportion functionally inserted in the screwthreaded portion (124) of theaxial hole (22), the screw (25) having a portion (27, 38) adapted tobear, during screwing, against a conical constriction (23) of the axialhole (22) and thereby expand the body (15).
 3. An anchoring deviceaccording to claim 1 wherein:the axial hole (22) has an internallyscrewthreaded rigid portion (124) with no longitudinal slots (24), theaxial core and the means for moving it axially comprise a screw (25),the screw having a shank, the shank having a screwthreaded portionfunctionally inserted in the screwthreaded portion (124) of the body(15) with the axial hole (22), the screw (25) having a conical portion(27) adapted to bear, during screwing, against the constriction (23) ofthe axial hole (22) and thereby expand the body (15).
 4. An anchoringdevice according to claim 3 wherein the screw portion (25) adapted tobear against the constriction (23) of the axial hole (22) is formed bythe distal end (27) of the screw (25) opposite the screw head (28). 5.An anchoring device according to claim 4 wherein the screw head (28) hasa polygonal cross-section with rounded corners forcibly inserted at theend of screwing into a proximal end portion (215) of the body (15)having longitudinal slots (216, 217) through it and a diameter less thanthat of the screw head (28).
 6. An anchoring device according to claim 2wherein the screw portion (25) adapted to bear against the conicalportion (23) of the axial hole (22) is formed by the proximal screw head(28) inserted in a corresponding proximal conical portion (23) of theaxial hole (22) in the body (15).
 7. An anchoring device according toclaim 1 wherein:the axial core (32) slides freely and longitudinally inthe axial hole (22) and is coupled to the body (15) by means (33) forpreventing axial rotation, the axial core (32) has a screwthreaded axialbore (34), a screw (35) with a screwthreaded shank (36) and a proximalhead (37) is inserted in the axial hole (22) in the body (15) with itshead (37) in axial bearing engagement against the proximal end (17) ofthe body (15) and with its shank (36) functionally inserted in thescrewthreaded axial bore (34) of the axial core (32) so that rotation ofthe screw (35) moves the axial core (32) axially and expands the body(15).
 8. An anchoring device according to claim 7 wherein the screw head(37) has a conical bearing face (38) engaged against a second conicalportion (39) of the axial hole (22) associated with second longitudinalslots (F2) constituting a second expandable portion of the body (15). 9.An anchoring device according to claim 7 wherein the axial core (32) hason its peripheral surface a radial immobilizing lug (33) inserted in oneof the slots (24) of the body (15) to prevent it rotating.
 10. Ananchoring device according to claim 1 wherein the peripheral sidesurface (16) of the body (15) has anti-slip projections opposing axialsliding of the body (15) in the hole (7) in the bone tissue and opposingrelative axial sliding between the body (15) and the end (5) of theligament (4).
 11. A ligament prosthesis comprising an anchoring deviceaccording to claim 1 inserted side by side in a hole (7) in the bonetissue with a bone rod (5) forming the end of a ligament (4).
 12. Aligament anchoring device for fixing an end of a ligament to a bone,comprising:an elongate body, delimited by a peripheral side surface, aproximal end, and a distal end, a longitudinal axial hole in the body,the axial hole being open at least at said proximal end, at least oneinterior constriction of the axial hole, longitudinal slots through thebody and distributed around a perimeter of its peripheral surface atleast in a vicinity of an area occupied by the constriction of the axialhole, an axial core housed in the axial hole in the body and movablelongitudinally to bear against the constriction of the axial hole on acontact surface adapted to expand the body in response to movement ofthe axial core, and means, accessible from the proximal end of the body,for selectively moving the axial core in a longitudinal direction,wherein a generally flat lateral bearing face forms a part of theperipheral side surface of the body and is adapted to bear against aside of the end of the ligament inserted side by side with the body in ahole in bone tissue opening onto an exterior surface of a bone, andwherein the peripheral side surface of the body has a generally constantcross-section throughout its length.